STUDIES ON THE COMPAEATIVE ANATOMY OF SPONGES. 253 



EXPLANATION OF PLATES 10—14, 



Illustrating Dr. Dendy's paper " Studies on the Comparative 

 Anatomy of Sponges." 



Note. — The majority of the drawings have been made from parafiBn sections 

 of ordinary spirit material, and in most cases a camera iucida has been 

 employed. 



In Figs. 1 — 22 the collared cells are diagrammatically represented by red 

 dots, and the outlines of the spicules are drawn in blue. 



Reference Letters, 

 calc. Calcoblast. c. c. Collared cell. c. g. c. Central gastral cavity. 

 eh. di. Diaphragm of exhalant opening of flagellated chamber, d. cor. Dermal 

 cortex, d. p. Dermal pore. eci. ep. Ectodermal pavement epithelium, emb. 

 Embryo, emb. c. Embryo capsule, end. ep. Endodermal pavement epithe- 

 lium, ex.c. Exhalant canal, ex. op. Exhalant opening of flagellated chamber. 

 Jl. ch. Flagellated chamber, fl. ch. x. Flagellated chamber in the contracted 

 condition, g. cor. Gastral cortex, g. q. Apical ray of gastral quadriradiate 

 spicule, projecting into the central gastral cavity, i. c. Inhalant canal. 

 mus. c. Muscle cell. osc. Osculum. ov. Ovum. pros. Prosopyle. s. d. q. Sub- 

 dermal quadriradiate spicule, s. d. s. Subdermal sagittal triradiate spicule. 

 s. g. s. Subgastral sagittal triradiate spicule, s. m. SoUas's membrane, sp. 

 Spicule, sp. s. Spicule sheath (formed from the gelatinous ground substance 

 of the mesoderm), st. c. Stellate mesoderm-cell. t. ox. Tuft of oxeote 

 spicules at the end of a radial chamber. 



PLATE 10. 



Fig. 1. — Leucascus simplex. Portion of a vertical section, passing, on 

 the left, through the osculum. Drawn under Zeiss A, ocular 2. 



Fig. 2. — Sycon Carteri. Portion of a transverse (horizontal) section, 

 showing three of the radial chambers. Drawn under Zeiss C, ocular 2. 



Fig. 3.— Sycon gelatinosum. Portion of a longitudinal (vertical) sec- 

 tion, passing through the distal ends of the radial chambers. Drawn under 

 Zeiss C, ocular 2. 



Fig. 4. — Sycon gelatinosum. Portion of a longitudinal (vertical) sec- 

 tion, passing through the proximal ends of the radial chambers. Drawn under 

 Zeiss C, ocular 2. 



